UBC Theses and Dissertations
Addition polymerization of phosphorus-carbon double bonds Yam, Man Sheung Mandy
The distillation of phosphaalkene MesP=CPh 2(I, Mes = 2,4,6-trimethyiphenyl) has afforded poly(methylenephosphine) (II) in the residue with a molecular weight of ca. 30,000 gmo1−¹. Polymer II can also be obtained using radical and anionic initiators. The backbone of polymer II consists of phosphine moieties which can be chemically functionalized using hydrogen peroxide and elemental sulfur to afford air-stable polymers [-MesP(=O)CPh₂₋] and [-MesP(=S)CPh₂₋],respectively. The thermogravimetric analyses (TGA) of these polymers showed a high thermal stability to weight loss (Tonset = ca. 300 °C). Using the base-catalyzed phospha-Peterson reaction, we have synthesized several P-Mes phosphaalkenes including MesP=C(4-FC ₆H₄)₂(III), Me5PCPh(4-FC₆H₄)(IV), MesPC(4- MeOC₆H₄)₂(V), MesP=CPh(4MeOC₆H₄)(VI), and MesPCPh(2-pyridyl) (VII). X-ray quality crystals were obtained for phosphaalkenes III, VI, and VII. Attempts to prepare P-adamantyl (P Ad) phosphaalkenes with this method were unsuccessful. In an attempt to prepare AdPCPh ₂, the product isolated was found to be a 1 ,2-diphosphetane (AdPCPh₂)₂ by X-ray crystallography. The effects of reaction temperature, residence time, and initiator loading on the radical polymerization of I were studied. The polymerization conditions of 1% VAZO 88 initiator [1,1’- azobis(cyclohexanecarbonitrile)] at 100 °C for 24 hours are shown to give a higher molecular weight (M = ca. 16,000 gmo1−¹) and yield for II for radical polymerizations. Employing these conditions, phosphaalkenes Ill—WI were polymerized to give C-functionalized poly(methylenephosphine)s with molecular weight in the range of 6,000 to 20,000 gmo1−¹. The radical copolymerization of phosphaalkenes with styrene offers a convenient route to incorporate phosphine moieties into organic polymers. Preliminary estimation of the monomer reactivity ratios for phosphaalkene I and styrene was conducted using Fineman—Ross and Kelen-Tudos methods (rpA ≈ 2 and rsT ≈ 1). This study suggests that this copolymer may consist of poly(methylenephosphine) sequences, randomly, distributed between styrene moieties. To expand the addition polymerization to other PC systems, several new P-fluoroaryl phosphaalkenes were prepared using base-induced 1,3-hydrogen rearrangement. Employing 2,6- bis- or 2,4,6-tris-(trifluoromethyl)phenyl (ArF’ and ArF) substituents, the rearrangement reaction becomes a viable route to isolable phosphaalkenes with a C-methyl substituent (i.e., ArF’P=CMe₂, ArF’P=CMePh, and ArP=CMe₂).
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